1. Field of the Invention
The present invention pertains to a door safety circuit for the monitoring of at least one story door of an elevator or lift installation, which circuit includes a transmitter and a receiver, wherein a non-electrical signal, produced by the transmitter and influenced by a latching device of the story door, is conveyed to the receiver for conversion into an electrical signal.
2. Discussion of the Background of the Invention and Material Information
French Patent Publication FR 1 432 651 discloses a safety circuit in which a door latch, monitored by means of a photo-electric device, is used for lift or elevator installations. A light beam emitted by the light source of a photo-electric device arrives, in case the door latch displays a certain setting, at a photo-sensor, with the electrical signal thereof being passed onto the lift or elevator controller.
A disadvantage of the noted device resides in the fault susceptibilities of the transmitter and the receiver, which are exposed to shocks during each latching movement and are thereby subject to excessive stresses.